The present invention relates to rotors for caliper disc brakes and the like, and in particular to a composite construction therefor.
Rotors are generally well known in the art, and are used extensively in caliper disc brakes, power transmission devices, clutches, and other similar machinery and mechanisms. Brake rotors are typically cast from a ferrous material, such as cast or grey iron, and are then machined in multiple operations to shape the rotor, to form a inner hub portion and friction surfaces. The inner hub portion of the rotor is mounted to a drive member, such as the vehicle axle, and is drivingly connected to the vehicle wheels. The friction surfaces of the rotor typically include oppositely directed friction surfaces which interface with associated brake pads for braking the vehicle. During braking, vibrations are created when the brake pads contact the friction surfaces of the rotor. Some of the vibrations are transmitted to the operator and passengers of the vehicle through the structure of the vehicle. The vibrations at the friction surfaces are transmitted through the rotor to the hub, to the axle and associated vehicle suspension components, and into the interior of the vehicle where they are manifested to the occupants as undesirable noise.
The ability of a brake rotor to quickly transfer and dissipate heat generated during the braking process is a very desirable feature, as excess heat leads to premature brake wear and/or failure. Also, the ability to readily match rotor and brake pad materials for a specific vehicle application is highly beneficial to achieve the desired braking performance at minimum cost. Corrosion is also a problem with cast iron brake rotors, particularly when used with spoked or windowed types of wheels in which rotors are normally visible, such that some rotors are painted or otherwise surface treated, which adds cost to the part. Weight is another drawback associated with most ferrous metal rotors. Cast aluminum rotors are available to reduce the weight and corrosion problems associated with ferrous metal rotors, however, the heat resistance and brake surface toughness of cast aluminum is typically less desirable than that of other types of rotors.
It is known to use composite rotors having combination of separate components including a friction portion and a hub portion, each comprised of different materials to provide a lightweight, corrosion resistant rotor as disclosed in Ihm (U.S. Pat. No. 5,509,510). However, such rotors use a combination of mechanical and metallurgical bonds to secure the rotor components together. The metallurgical bonds formed between the rotor components couples the components for the effective transmission of braking vibrations through the rotor, to the vehicle, creating noise for the people inside. It is desirable to reduce the transmission of vibrations between the composite rotor components to reduce the braking noise.